John Key says he is confident security for the Rugby World Cup will not be compromised by extending the deployment of the SAS in Afghanistan.

Prime Minister John Key has confirmed the New Zealand Special Air Service (SAS) deployment to Afghanistan will be extended for another year from April - but it will be around half the size of the current deployment.

NZ SAS soldiers fired weapons in self-defence when they killed two security guards in Afghanistan on Christmas Eve, an investigation by the NATO-led International Security Assistance Force and the NZ Defence Force has found.

Major General Lou Gardiner, the Chief of Army for three years until he retired last year after 39 years service, said he would back what the SAS troops said over anyone else.

The Defence Force insists that New Zealand SAS troops in Afghanistan involved in a fatal shootout were fired upon first.

The NZ Defence Force says SAS soldiers were acting in self defence when they led a raid on a factory in Afghanistan in which two soldiers were killed.

Labour's defence spokesman Pete Hodgson says it is 'sad' the SAS is fundraising for their families.

Defence Minister Wayne Mapp has ordered an immediate inquiry after reports businessmen paid for sessions with the defence force's elite Special Air Service (SAS) troops.

The identities of two soldiers injured in an Afghanistan insurgent attack overnight have been revealed.

The New Zealand soldier killed in Afghanistan overnight was a decorated officer who had been in the army for five years.

New Zealand's first combat death in Afghanistan is not a reason to withdraw our troops from the country, Prime Minister John Key says.

Maggie Tait, who visited Bamiyan in May, reflects on life on the New Zealand base there in the wake of its first combat death.

A New Zealand soldier has been killed and two others injured in an attack on a routine patrol in Afghanistan, the Defence Force announced today. A local interpreter with the patrol was also injured during the attack.

Murray McCully says Afghanistan's Bamiyan Province, where NZ troops have been since 2003, will be ready to stand on its own before Hamid Karzai's 2014 deadline.

The critically wounded SAS soldier whom Willie Apiata carried to safety under heavy gunfire was the personal bodyguard for John Key on his recent trip to Afghanistan.

Most New Zealanders want Special Air Service (SAS) troops withdrawn from Afghanistan, a poll has found.